A negative electrode active material including: a particle of negative electrode active material containing silicon-based material of SiOx (0.5≤x≤1.6); wherein the intensity A of a peak in a Si-region given in the chemical shift region of from −50 to −95 ppm and the intensity B of a peak in a SiO2-region given in the chemical shift region of from −96 to −150 ppm in a 29Si-MAS-NMR spectrum of the silicon-based material satisfy a relationship that A/B≥0.8. This provides a negative electrode active material which can increase a battery capacity, and can improve cycle characteristics and initial charge/discharge characteristics when used as a negative electrode active material for a lithium ion secondary battery.